As can be seen by reference to the following U.S. Pat. Nos. 263,634; 1,543,411; 1,793,246; and 3,583,555; the prior art is replete with myriad and diverse conveyor belt cleaning arrangements employing both mechanical and pneumatic cleaning elements.
While all of the aforementioned prior art constructions are more than adequate for the basic purpose and function for which they have been specifically designed, these patented constructions are not particularly well suited for, nor adapted for use in a high abrasive conveyor belt environment. A rigid scraper blade is required to come into compressive engagement with the conveyor belt surface to accomplish the cleaning of the conveyor belt, such as would be found in a mining situation.
A major contributor to the problem of short life expectancy for the blade type conveyor belt cleaners is uneven wear along the blade edge. Uneven wear results in the formation of channels in the blade edge which allows the passage of carryback between the blade and the belt. In an effort to reduce the uneven wear problem, the U.S. Department of Interior, Bureau of Mines, has undertaken a study of the mechanisms responsible for effective belt cleaning. From this study emerged a design for a cleaner blade that would greatly reduce uneven edge wear. The blade design consisted of a standard cleaner blade incorporating air passages which allow for the expulsion of air along that part of the blade edge which is in contact with the conveyor belt surface. Test results indicated that the expulsion of air on the blade edge prevents further development of the scratches into deep grooves. These tests showed that the effective blade cleaning life can be extended up to 100 times using the pneumatic cleaning blade when compared to tests using solid metal cleaning blades.
Conveyors are used throughout the mining and mineral processing industry for transporting high volumes of material over relatively short distances. Conveyors offer several advantages including: continuous material handling; good transport energy efficiency; low manpower requirements; and high material handling capacities. Several problems are inherent to conveyor transport. These include: conveyor adjustment (i.e. belt tracking); system reliability; and system spillage. The Bureau of Mines is examining these problems.
The problem of system spillage was recently examined. This research was designed to determine the mechanisms involved in the operation of blade type belt cleaners. A significant conclusion drawn in this research was that conveyor blades tend to wear unevenly for all types of blade material, and that wear preferentially occurs in regions of the blade not in direct contact with the belt. These blades included mild steel, tool steel, steel with ceramic inserts, and polyurethane. This research demonstrated that the blade wearout phenomena could be slowed by maintaining proper blade-belt pressures, by eliminating belt irregularities, such as metal splices or recessed belt logos, and by increasing blade hardness. With these suggested improvements, blade cleaning life could be approximately doubled, but maximum effective blade life was still generally less than one day under laboratory conditions. From this study, a design was conceived for a cleaner blade that would greatly reduce uneven edge wear.
As a consequence of the foregoing situation, there has existed a longstanding need particularly in the mining industry for a self-healing scraper blade construction which will prolong the useful life of cleaning scraper blades which contact conveyor belt surface, and the provision of such a construction is a stated objective of the present invention.